extern "C" { 
    #include "apue.h" 
}   
#include <stdio.h>

#include <limits.h>
#include <unistd.h> //sysconf

int main(int argc ,char** argv)
{    
    printf("max open fd number is %ld\n",sysconf(_SC_OPEN_MAX)); 

}

#if(0)
max open fd number is 1024
#endif
